1. Field of the Invention
The invention relates to a form for erosion control structures suitable for use along a shoreline, wherein fluid transmitting material is attached to the form for equalizing hydrostatic pressure developing between the form and the surface upon which the form rests.
2. Description of the Prior Art
In many instances, it is highly desirable to provide a shoreline with some type of structure for preventing the erosion of the shoreline by the action of waves and underwater currents. In the past, such structures have included concrete walls, beds of large boulders placed along the shoreline, or large concrete slabs lowered into the water upon the shoreline. In order to eliminate the many well-known problems attendant with the foregoing structures, it has been proposed to form a structure in situ along the shoreline in order to provide an erosion control structure.
Examples of this proposal are to be found in: U.S. Pat. No. 3,396,542, issued Aug. 13, 1968, to B. A. Lamberton; U.S. Pat. No. 3,425,228, issued Feb. 4, 1969, to B. A. Lamberton; U.S. Pat. No. 3,474,626, issued Oct. 28, 1969, to the present inventor; U.S. Pat. No. 3,520,142, issued July 14, 1970, to L. A. Turzillo; U.S. Pat. No. 3,524,320, issued Aug. 18, 1970, to L. A. Turzillo; U.S. Pat. No. 3,565,125, issued Feb. 23, 1971, to John T. Hayes; U.S. Pat. No. 3,570,254, issued Mar. 16, 1971, to L. A. Turzillo; and U.S. Pat. No. 3,837,169, issued Sept. 24, 1974 to B. A. Lamberton. In the foregoing patents, it has been proposed to use a fabric form comprised of two or more flexible sheets of material which are joined to form a space adapted to have a cementitious slurry injected therein. Those disclosed forms are placed upon the shoreline, or surface to be protected, and are then filled with the cementitious slurry, whereby a concrete revetment mat, or slab, is formed upon the surface to be protected from wave action.
A major problem encountered in using the foregoing forms of Lamberton is in providing some means for the relief of hydrostatic pressure which develops between the concrete mat and the surface upon which the mat rests. If the forms are not provided with means for relieving such hydrostatic pressure, the slabs produced by the foregoing patents can be moved by such hydrostatic pressure or washed away by the currents or wave action.
Turzillo utilizes a plurality of stakes to anchor his forms to the shoreline, a costly and time consuming operation. Alternatively, in U.S. Pat. No. 3,524,320, Turzillo relies upon excess cement grout oozing through his form into the surface upon which the form rests, whereby the form is bonded to the surface below the form. It is believed that this approach does not sufficiently provide an adequate anchoring means for the form, nor is there any provision disclosed for the relief of hydrostatic pressure developing beneath the form.
In the other forms disclosed in the foregoing patents, with the exception of U.S. Pat. No. 3,837,169, the forms are provided with a plurality of openings throughout the forms to provide for relief of hydrostatic pressure. A major problem associated with those openings is that they can become clogged with the growth of underwater plant life, whereby they become ineffective to relieve hydrostatic pressure developing beneath the form. Additionally, the soil and rocks beneath the form may tend to clog those openings. Accordingly, in my prior patent, I proposed the use of a filter cloth beneath the openings to prevent soil and rocks from clogging those openings. However, such openings could still become clogged from the growth of underwater plant life.
Furthermore, another major problem with forms having openings formed therein is that the areas surrounding those openings are areas of structural weakness in the form. These areas of structural weakness, or stress points, are subject to ripping open due to the exertion of pumping pressure forces during the filling operation of these forms. If such damage occurs to the form, it cannot be properly filled, nor will an effective erosion control structure be formed upon the underwater surface.
Accordingly, prior to the development of the present invention, there has been no form available for erosion control structures which adequately provides for equalizing hydrostatic pressure developing between the form and the surface upon which the form rests. Therefore, the art has sought a form for erosion control structures which adequately provides for equalization of such hydrostatic pressure, absent the problems of previously proposed forms.